Questions tagged [radio-frequency]

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What type of equipment could generate interference on the 1.6ghz spectrum [closed]

From the perspective of physics - other than wireless computer network devices - what domestic or domestic or commercial equipment could generate seemingly random interference on the 1.6ghz range? ...
1 vote
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How do lasers work if the phase shift from reflection is 180 degrees?

I am having a hard time wrapping my head around the phase shift that is imposed by reflection. I'm specifically thinking about things like visible light of off mirrors or RF reflecting off of silver, ...
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If we have a cosmic microwave background should't we also have a cosmic radio wave background?

I'm a layman in physics, but here is what I understand: What we see in the sky with naked eyes is a map of electromagnetic waves in the frequency visible to the human vision. But that kind of ...
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Reflection of power at low frequencies?

Assume you have an AC signal source outputting 0dBm of power and connected to that are two resistors one of 50 ohms and another 100 ohms. The reflection coefficient is given by: It seems like this ...
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1 answer
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How does the echo of a radio wave from Venus depend on the rotation speed and direction of the planet?

In this paper from around 1960 scientist used echos of radio waves from the Venus' surface to determine its rotational speed and direction. How can the rotation of Venus affects the echo of the radio ...
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On synchrotron oscillations

Citing from Buckets and Bunches: taking a closer look at LHC: Imagine two particles in a bunch: particle $A$ which has energy (or momentum) corresponding properly to the RF frequency, and particle $B$...
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4 answers
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Why do we even need RF cavities to accelerate particles?

Wouldn't it be easier to just apply a constant $E$ field along the beam axis? This would avoid all kinds of problems like synchronicity, phase change etcetera. Addendum. What puzzles me the most is ...
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Is there any mathematical model of how does rain & other weather conditions impact the radio link?

I'm looking through UAV radio-communication process and wondering if there are any formulas, describing how does the air pressure and weather itself (rainy & snowy conditions) affect the radiolink ...
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Radiowave diffraction

When a far field propagated radio wave encounters an obstacle such as a mountain does the radio wave actually bend around the mountain? In other words should my receiving antenna on the other side of ...
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Superposition of EM waves and "magic" behind tuned receiver circuit

I'm struggling to understand how the receiver circuit (eg. FM radio) is able to extract a particular frequency out of the sum of all received frequencies by its antenna? I've checked dozen of websites,...
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Hypothetical NMR experiment

Say I set the RF of NMR to resonate to a specific frequency of a specific isotope of nitrogen, based on the magnetic field strength of the NMR machine, Now, imagine if I had put in egg whites(or any ...
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Wireless Power Transfer in Layered Material

I’m looking to develop a mathematical model for near-field electromagnetic power transfer through layers of human tissue, from an external transmitting antenna to an embedded antenna. Each tissue ...
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1 answer
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Frequency upconversion of pulses shorter than 1 IF period

I have a rather elementary frequency upconversion/mixer question, perhaps so simple that it does not warrant a real question but rather just a reference to a website/tutorial (that I have not been ...
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How are sidebands generated in an AM signal?

I can't understand how sidebands get generated, even after reading this wikipedia page: https://en.wikipedia.org/wiki/Sideband#Amplitude_modulation This is how I picture Amplitude Modulation in its ...
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Scattering off upside-down parabolic reflector (radio frequency)

Suppose I have a steel frame parabolic reflector with a handful of steel wire supports. The size is approximately 10m high and 20m in radius. Assume the gaps in the triangular trusses are roughly 3m. ...
8 votes
1 answer
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Why is a magnesium flame changing color in an electromagnetic field?

On YouTube I have seen someone build a RF emitter (probably in the 10 MHz range with about 5000 Watts) and then use it to ignite magnesium strips. Magnesium usually burns with a bright white flame in ...
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Do electrons in EM waves literally travel in space, or they just move like a rope being swung at an end

Electrons do actually move in a closed circuit as explained in this video: https://youtu.be/8gvJzrjwjds?t=85 They jump from atom to atom. But what about electromagnetic waves, or more specifically ...
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How would an AM and FM wave change when the input signal increase in loudness or frequency?

I am currently studying for the A levels and am a bit confused about how an AM and FM wave will change when the wave isn't sinusoidal and have differing frequency and loudness. I understand how a ...
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Why are smartphone antennas not $\lambda/2$ of the wavelength? Why are patch-antennas used instead of simple dipole antennas? [closed]

Why are smartphone antennas not $\lambda/2$ of the wavelength? Why are patch-antennas used instead of simple dipole antennas? I'm very new to this but really interested in using basic physics to ...
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1 answer
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Can radio waves be converted to positron and electron when placed in weak electric field?

In particle physics, gamma rays can be converted to positron and electron when placed in strong electric field. My question is: What will happen if radio waves are placed in weak electric field? Will ...
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Can we express Free-space path loss formula in the following pointwise way?

We know that the Free-space path loss formula is of the form $$\frac{P_{r}}{P_{t}}=D_{r}D_{t}\left(\frac{\lambda}{4\pi d}\right)^{2} $$ $D_{r}, D_{t}$ are the directional gains of the receiver and the ...
1 vote
3 answers
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What are the advantages of radio spectroscopy? [closed]

What is the main purpose for radio spectroscopy? What information of the atomic structure of atoms can we gain from using radio frequency radiation rather than X-rays? Since the wavelength of radio ...
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Over what distance might this device be able to interfere with car radios?

I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
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Theoretically, could radio waves carry enough energy to destroy bacteria or viruses by resonance?

I've been reading recently about a mysterious and possibly hokey medical device of the 1930s. It was a variable-frequency radio emitter, invented by a Dr. Rife, which was supposed to kill various ...
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1 vote
1 answer
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What happens to Langmuir waves at a density gradient in plasmas?

I'm trying to understand a little bit of what happens to electrostatic Langmuir waves when there is an initial density gradient present. The plasma frequency depends on the density, so you would ...
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2 votes
1 answer
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Is it okay to sleep with the wifi router next to me?

Where I sleep I have my wifi router right above me. I don't know if this is safe for my health since it emits radiation. Some people say that it should be safe since the radiation emitted is non-...
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Why does amplitude modulated wave take the frequency of a carrier signal when passed through air?

If a message signal of frequency $f_m$ is amplitude modulated with a carrier signal of frequency $f_c$ and radiated through an antenna, the wavelength of the corresponding signal in air is ans: $\frac{...
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1 answer
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Radiowaves and electromagnetic waves

I have a simple question: What part of physics study radiowaves and electromagnetic waves? Can you link a source where can I find basics of radiowaves pdf or something?
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Single photon radio wave [duplicate]

If there is a single photon representing a radio wave with wavelength say 10 m, what does this 10 m really mean? Does it mean that the photon itself could be anywhere in those 10 m?
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Multipoint impedance matching to RF plasma

When dealing with RF plasma sources - one of the most significant challenges is impedance matching between RF power source and plasma. Impedance of plasma changes dramatically during ignition - and ...
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2 votes
1 answer
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What is the explanation behind radio shadowing by people?

I called it shadowing but masking may be more appropriate, feel free to suggest a better question title after you read the following. I have an old clock alarm radio receiver that plays at the center ...
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1 answer
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What is the most accurate instrument which can be used to measure frequency of radio waves without measuring wavelength and how accurate is it?

I wanted to know if there's an instrument that accurately measures the frequency of radio waves as I'm working on something and I didn't get anything good on web.
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X-rays are absorbed by bone. If the width of the bone increased in proportion to the wavelength, would bone absorb radio waves?

What I’m interested in here, are the properties of different electromagnetic waves, and the factors that cause them to be absorbed by different materials and be influenced in other ways by different ...
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What causes the sudden change in atmospheric reflection of long-band radio waves?

This picture shows up a lot. The explanations that tend to accompany it say that the long-band radio waves above ~10m are reflected, whereas other wavelengths are scattered or absorbed or transmitted. ...
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is room temperature quantum (qubit) nuclear magnetic resonance possible?

I know it is possible to do room temperature NMR. Not just that but one can also use the earth's magnetic field for the nuclei to precess about. If done this way, one gets precession at about the KHz ...
12 votes
3 answers
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How does the human body affect radio reception?

My sister asked me why her small radio sometimes has better reception when she places her hand nearby (without touching) the antenna. I did some research and wanted to ask a few questions. Here are ...
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Lens Design 60GHz Radar

I'm trying to design a lens for a 60GHz radar chip however rather than focusing the radar beam I'd like to widen it to a specific width. Also, the radar antenna has a main beam width that is larger ...
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2 votes
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How are phased arrays compatible with the photon concept?

Not a physicist (although I know how to develop and simulate phase arrays). Phased arrays are e.g. emitters sending waves with individual elements with a different phase so that they act ...
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Extreme Redshift Detection

There is a new paper in arXiv postulating that black holes might actually let some let some light out. This of course is very theoretical, but it postulates that the light would be redshifted to 640 ...
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1 answer
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How do the arc and the straight line have equal length in this figure?

I have the following derivation in one of my physics problem related to range of a transmitting antenna: How is the distance QT equal to the length of arc PT? Can someone provide a quick explanation ...
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2 answers
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Why do artificial transmissions of coherent EM waves tend to be isotropic at radio frequencies but directional at visible frequencies?

This is a somewhat soft question, and I'm far from an expert on the subject, so it's possible that my premise is factually incorrect. The practical generation mechanisms for useful real-world coherent ...
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Doubt in radar question

This is a question(2.25) from introduction to radar systems by Merrill Skolnik 3rd edition. Plot the single-scan probability of detection as function of range, assuming a constant cross-section target ...
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Building a radio telescope!

So, I saw recently the idea of a radio telescope and thought how simple they are. So, like any other normal human being, I went on google and searched "how to make a radio telescope" and ...
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1 answer
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Is there a frequency converting amplifier? [closed]

Frequency conversion means output of the amplifier is at a frequency different from that of the input.
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What are odd radio circles (ORCs) in Space?

There is a video (https://www.youtube.com/watch?v=jXnXbMcI8Lo&t=595s) about pure radio waves radiating in circles in space. Odd radio circles (ORCs) are not radiating any other wave length (...
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Complex reflection coefficient for a radio frequency wave

With an RF transmitter at location $P_1$ and a receiver at $P_2$, I would like to calculate how much power reaches $P_2$ via a reflection at a point $P_3$. Hence I need to know the reflection ...
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Proxima Centauri radio signal

I have recently seen an article about an unusual radio signal coming from Proxima Centauri region. I understand there is a debate around the nature of this signal. My question is related to this ...
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How does UWB enable much higher positioning accuracies than Narrowband

literature and internet articles often only explain UWB’s much higher positioning accuracies with its much higher bandwidth compared to the bandwidth of other narrowband technologies such as WiFi/...
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Is it possible to filter radio-waves using another radio telescope?

When making an observation using a radio telescope, is it possible to filter out noise coming out from a known source by using another telescope that will focus on that noise source? By filtering, I ...
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How does oxygen react to radio waves at 60Ghz?

Since there are 3 states of oxygen: 3Σ−g: The ground triplet state 1Δg: The ground singlet state 1Σ+g: An excited singlet state. What happens to the ground triplet state when it is exposed to the 60 ...

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